GB2141652A - Method of spin-flanging a hollow, thin walled cylinder - Google Patents

Abstract

A spin flanger, for flanging a necked-in can body (A) has an axially and rotationally movable head (20) provided with a freely- movable pilot (30) for entering a pre-formed neck to align the can body (A) with the spin head (20). Spin-forming rollers (27), mounted on the periphery of the head, are rotatable on axes normal to the head rotation axis and each has a rim and body portion with meeting surfaces making an included angle of e.g. 120 DEG , the rim in use initially flares the end edge of the can body and the body portion (which extends substantially normally to the head rotation axis) completes the spin-formed flange. The head is cammed towards the can body and spin forming is accomplished while the head is moved by the cam at constant velocity. <IMAGE>

Description

1

GB2 141 652A

1

SPECIFICATION

Method of spin-flanging a hollow thin walled cylinder

5

The present invention relates to a method of spin-flanging a hollow, thin walled cylinder, useful for example, in can manufacture.

More particularly, the present invention is 10 concerned with a method of applying flanges to a drawn and ironed (D&l) container, i.e. the so-called 2 piece beverage can. D&l refers to the process used to manufacture the container. A shallow metal cup is drawn from a 15 thin metal sheet and then punched through a plurality of ironing rings which thin the wall without substantially reducing the diameter. During this process the wall of the container is reduced to about one third of its original 20 thickness, thus leaving a cylindrical container shell open at one end with a thinner side wall than bottom. At its open end the shell is trimmed to the right length and square with respect to the axis of the container. It is at 25 this stage that the container is first necked and then flanged such that the container may be thereafter double seamed with a can end, during a closure process after filling.

D&l containers are generally made out of 30 aluminum or tin-plated steel and during the ironing process the metal is substantially worked, particularly in the side wall and thus the hardness of the material increases and ductility decreases. Consequently, there is a 35 potential for the metal to be overworked to the point of failure. One mode of failure is cracking of the outer periphery of the flange. More particularly, a radial crack occurs in areas of the flange where the metal has an 40 inclusion or a weak point.

For many years containers have been drawn and ironed from low temper (T, and T2) box annealed tinplate steel. This metal has operated successfully in providing the required 45 combination of strength, hardness and ductility, such that flange cracked cans could easily be kept below a predetermined number per thounsand. It has been found to be more desirable to use higher temper metals to man-50 ufacture D&l containers. These higher temper materials can be used in thinner gauges to permit a greater number of containers to be made per pound of steel and yet the performance and strength of the container so pro-55 duced is equivalent to or better than thicker gauge cans.

In experimenting with higher temper materials of thinner gauge, it has been found that the D&l process can be applied without 60 much difficulty except for flange cracking. Techniques for overcoming the flange cracking problem include, inter alia, re-annealing before flanging and flanging to a shorter flange length or angle. All of these ap-65 proaches have their disadvantages and limitations.

The usual method of flanging uses a commercial flanging head having cones carried to rotate about their axes parallel to the axis of rotation of the total head. The tool is carried on a necker-flanger machine and is brought into the open end of the trimmed D&l container shell. The cones are rolled and moved against the upper inside edge of the container shell in such a way that the open end is flared outwardly to give the necessary flange configuration for an effective double seam. Use of this type of commercially available flanging head has produced about three times as many cracked flanges per thousand containers with higher temper materials than with the low temper steels or the softer aluminium materials.

We have been seeking to develop an improved method suitable for flanging, on high speed commercial equipment, higher temper metals of thinner guage than hitherto and to minimize the amount of flange cracking incurred. In the course of our work, we have refined the parameters of a new flanging head such that the number of cracked flanges per thousand cans spin flanged are reduced to a minimum.

We have, accordingly, adopted a new approach to a commercial flanging head for D&l containers; the new head is disclosed and its operation is explained herein.

In a periodical called Tooling and Production dated October 1978, two researchers from the U.S. Steel Corporation disclose their experimental, inclined-axes flanging head. The improvements of the present disclosure are adapted to that device and, more specifically, are included to make that device operate in a commercial environment. That is to say, that the improvements herein were necessary in order to make that experimental device suitable for high speed commercial operation on a necking and flanging machine. The U.S. Steel device includes a head having six rollers disposed radially about the head, each being mounted for rotation about an axis normal to that of the head. The spin flanging device as proposed by U.S. Steel Corporation caused the end of the container to crush when used in a commercial necker-flanger, producing a ripped or fluted flange totally unacceptable for use in a double seam with a can end closure.

Three specific improvements were responsible in practice for producing an acceptable flange and for minimizing the number of cracked flanges per thousand. A piloting device was added to the drive axis of the inclined axes spin flanging head. The piloting device guides the can as it approaches the rollers, each of which is supported on an inclined axis. Without the piloting device the axial orientation of the container shell in a commercial necker-flanger was not certain, and container shells could be taught between

70

75

80

85

90

95

100

105

110

115

120

125

130

2

GB2141 652A 2

the roller and the body of the flanging head. In addition, the pilot aids in forming a more uniform flange because it holds the can in a central position relative to the spin flanging 5 rollers.

The roller configuration disclosed in connection with the experimental U.S. Steel Corporation head included a large diameter rim section with a smaller central hub. The rim 10 section splayed away from the hub such that the surface of the rim section interesected the axis of the hub at an angle of about 70°. It has been found that angles of 120° to 150°, and preferably 120° for the inclination be-15 tween the hub and rim, are required in order to keep the rollers from interfering with the neck of the can. The radius between the hub and rim should be from about 0.070 to 0.090" (1.78 to 2.28 mm).

20 Our third modification to adapt and use an inclined axes spin flange head with a commercial necker-flanger relates to the way in which the flanging head is used. Commercial necker-flangers include a camming device which 25 moves the flanging head or the container shell axially for contact with the flanging rollers. The camming device is designed to assure that the flanging rollers contact the can during a constant velocity portion of the cam profile. 30 We have found that any acceleration during the critical contact portion of the spin flanging operation will cause the flange, to crush developing a rippled or fluted surface.

It is found that the inclined-axes spin flang-35 ing head disclosed herein minimizes residual stress in flanges by providing gentler, smoother and more constant flange-forming operation well suited to the harder temper materials which can be used in thinner gauges 40 for fabricating D&l cans.

According to the present invention, there is provided a method for spin flanging a hollow thin walled cylinder, including the steps:

(i) arranging an inclined axes spin flanging 45 head for rotary and axial movement in alignment with the axis of the hollow thin wall cylinder,

(ii) supporting said cylinder in axial alignment with said rotary axis of the spin

50 flanging head,

(iii) moving the spin flanging head axially into engagement with an open end of said hollow thin wall cylinder with a constant velocity, and then spin-forming the end edge of

55 the cylinder by

(iv) engaging rollers mounted to rotate on said inclined axes with the said edge of said cylinder, the rollers including surfaces which, in the course of the said constant velocity

60 movement, first flare and then radially form a flange on the said edge.

Benefically, the cylinder is maintained in axial alignment with the rotary axis of the head, as the cylinder and head are moved into 65 engagement for spin-forming, by bringing a freely rotatable pilot at a leading end of the head into the open end of the cylinder, there being a clearance between the pilot and the inside wall surface of the cylinder of about 0.010" (0.25 mm).

The invention will now be described in more detail by way of example with reference to the accompanying drawings, in which:

Figure 7 is a side cross-sectional view of a prior art commercial spin flanging head.

Figure 2 is a side cross-sectional view of the inclined axes spin flanging head according to the present invention.

Figure 3 is a schematic illustration of the camming which takes place in moving the container into the spin flanging tool, and

Figure 4 is a fragmentary cross-sectional view of a roller shown in the flanging head illustrated in Fig. 2.

As background for the complete understanding of the invention a brief description of a necker-flanging machine in which it is used will be included. We, American Can Company, manufacture and sell a Model 201-862 necker-flanger machine. The purpose of the machine is to accept a pretrimmed 2-piece D&l container shell and first neck its upper end inwardly and then bend outwardly a flange for doubleseaming. Necking is necessary for several reasons, one of which is to keep the outside diameter of the doubles-earned container uniform so that the container can easily roll through processing plant equipment. By necking the container, the overall diameter of the subseqsuently doubleseamed end can be made identical to or less than that of the body. In certain instances it is even useful to double-neck fthe open end of the container such that an end of smaller diameter can be applied. This helps in lowering the cost in that the amount of material necessary for the end is reduced. Another aspect of necking in a container, which relates somewhat to flange cracking, is the ability to limit the radial extent of the distal portion of the flange so that the circumferential stresses in the metal about the periphery of the flange are kept to a minimum. The machine for necking and flanging carries container shells on their sides by a series of turrets which are mounted on a horizontal axis. Each turret carries the container shell in position such that relative axial movement is permitted between it and the tools which operate to perform necking or flanging functions. For aluminium cans, the steps of the operation are necking and then flanging. For the harder steel cans, the machine pre-necks them on a first turret, further necks on a second turret and finally flanges on the last turret.

As is evident by the foregoing, the harder the metal the more susceptible the container flange is to cracking. In the preferred embodiment, material such as T-4 temper continuously annealed tinplated steel is used. This

70

75

80

85

90

95

100

105

110

115

120

125

130

3

GB2 141 652A

3

material is much harder and stronger than that heretofore used. For an example, the T-1 containers were made from a 103 # plate. This terminology is standard in the can mak-5 ing industry and refers to the amount of steel in a base box of tinplate. A base box is a package of 112 sheets of steel 14" by 20" (35.5 by 50.8 cm) or a total of 31,360 square inches of area on one side (20.2 sq. 10 metres). Since steel is sold by the pound weight the base box convention is a shorthand means by which the weight of the material used is designated. By going to the harder T-4 temper material, tinplate of 95 # per base 15 box weight (95 lbs or 43 kg) can be used to make containers of equal or greater strength than those fashioned from T-1 103 # plate (103 lb or 46.7 kg). The impact of the gauge reduction with the same size blank is best 20 appreciated with respect to an understanding that the T-4 95 # tinplate steel allows the manufacture of one extra container per pound of steel or roughly 95 additional containers per base box. This of course, implies that the 25 extra hardness and reduction in ductility does not add additional cracked flanges which would cause the additonal containers to have to be scrapped.

The improved flanging head of the present 30 disclosure has been found to produce, in a commercial environment, the lighter gauge higher temper containers with no more than the standard number of cracked flanges per thousand containers, i.e. no more than the 35 number obtained with the standard T-1, 103 # plate.

Turning now to Fig. 1 a cross-sectional view is given of the prior art flanging head 10, carried on a necking/flanging machine (not 40 shown) by a holder 11 which rotates and moves axially in and out in accordance with a cam (also not shown). However, profile for cam movement is shown in Fig. 3 and will be discussed in detail later. The holder 11 carries 45 a plate-like support or cone holder 1 2 designed to support a plurality of ball bearings 13 for each of the cones 14 such that they may rotate about axes parallel to that of the holder 11 on the ball bearings 13. Each cone 50 14 has a chamferred lead area 14a and a necked-in support shoulder 14b whereby the container A is flanged when the cone 14 meets with the necked-in container A due to the axial movement of the flange head 10, 55 the spinning motion of the cone holder 12 and the rotating motion of the individual cones 14. There are four or five of such cones 14, depending on the inside diameter of the can, arranged (in Fig. 1 only three are shown) 60 so that the container A is formed during the operation which moves the spin flanging head 10 axially into the open end of the necked container A. The parallelism between the axes of the 14 and the holder 11 is apparent from 65 the description and Fig. 1.

In Fig. 2 the inclined axes spin flanging head 20 of this invention is shown. The head 20 includes a holder 21 including hub portion 21a designed for mounting a yoke 22 by means of bolts 23 which extend through the light portion 22a of the yoke 22 and into the hub 21a of the holder 21. The yoke 22 has a pair of inner and outer legs 24a and 24b respectively which are spaced apart and carry a stud 25 which is mounted to be radically disposed with respect to the hub 21a and is inclined to the axis of holder 21, preferably at 90° thereto. Stud 25 supports a pair of axially spaced apart roller bearings 26 carried inside a roller 27 for rotatably supporting the roller

27 relative to the stud 25 between the legs 24a and 24b of yoke 22, see Fig. 4 as well. There is a plurality of such rollers 27 radially disposed about hub 21a such that they function to engage a container brought axially to bear against them. Each roller 27 of the six rollers 27 on the preferred embodiment has a rim portion 28 and a hub portion 29. The angle B between the surfaces of the rim 28 and the hub 29 is critical to the performance of the roller 27. This angle should be greater than 110° and no more than 150°, preferably about 120°. The radius between the intersection of the surfaces of the hub 29 and the rim

28 should be between 0.070 and 0.090" (1.78 to 2.28 mm).

In the center of hub 21a is a hollow recessed portion 21b designed to receive a pilot 30 axially disposed to rotate freely with respect to the inclined axis spin flanging head 20. The pilot 30 is secured axially by a shouldered mounting bolt 31 which carries a pair of spaced apart ball bearings 32 that support a flanged pilot 33. Pilot 33 includes a central outwardly extending mounting portion 34 adapted to cooperate with the bearings 32 and fit within and be received by recess 21b such that portion 34 is capable of rotating about the same axis as that which the in-clined-axes spin flanging head 20 rotates about. The outer radial periphery 33a of the flange portion of pilot 33 is shaped to receive the inside diameter of a container shell across the necked-in portion with a clearance of 0.010" per side for supporting and guiding the end of container shell A into cooperative engagement with rollers 27 during the flanging operation.

From the foregoing, it will be seen that the rollers 27 rotate about axes inclined with respect to the rotation axis of holder 21 (e.g. at 90° thereto), in contrast to the prior art where the cones 14 rotate about axes parallel to the holder rotation axis.

Fig 3 is a schematic representation of the cam path used in connection with the movement of the inclined axis spin flanging head 20 of Fig. 2 into the container A. at each end of the schematic diagram the cam follower C is shown phantom in its retracted position.

70

75

80

85

90

95

100

105

110

115

120

125

130

4

GB2141 652A 4

The cam is a groove cut into the edge of a circular disc (not shown) which groove has varying axial positions such that it can activate the follower to move the inclined spin flanging 5 head 20 of Fig. 2 to and from the container shell A. Going from the right in Fig. 3 to the left, we traverse the groove of the cam as the disc rotates through 360° while the follower moves in accordance with the path shown. 10 More specifically, the movement of the rollers 27 to and from the container A is represented by the vertical movement of the follower C shown in phantom, and the rotation of the cam is linearly set out from right to left on the 15 camming time diagram, Fig. 3. At the top of the schematic drawing the individual segments of the cam action are specified in degrees for each segment; at the bottom the total degrees of rotation travelled from zero to 20 360° are specified. From zero to 45° of rotation starting from the right and going to the left, we have a period of dwell wherein the inclined axes spin flanging head 20 is retracted and held apart from the container A. 25 From 45° to 85° there is a harmonic rise on the cam such that spin flanging head 20 is brought quickly into position for contact with container A. From 85° to 95° there is a modified cycloidal motion which is substan-30 tially constant in velocity but is designed to bring the head 20, i.e., rollers 27 into contact or engagement with the container A, to begin the flanging operation. For the following 100° there is continual constant velocity increase in 35 movement such that the rollers 27 are throughout the entire 110° of rotation (from 85° to 195°) moved about 0.0078" (0.02 mm) per degree of cam rotation toward the container A; the last 10° from 185° to 195° 40 is in modified cycloidal in nature. For the next 20°, i.e. from 195° to 215° the lifted position of the follower C is in a dwell state such that the rollers 27 are held against the now outwardly formed flange of container A. This 20° 45 of dwell is necessary in order to set the flange and overcome any tendency to spring back. It takes 50° more, from 215° to 265° of rotation for the cam follower C to retract the head 20 or cause the same to fall away from the 50 container A and this motion is harmonic in order to speed the retraction. The rest of the rotation of the cam or 95° is for dwell and extends to the initial 45° of dwell. Without constant velocity during the flange spinning 55 operation a fluted or rippled flange will be generated.

While a specific high temper material of a given plate weight and material has been described in connection with the preferred 60 embodiment and while a particular American Can Company necker flanger has been explained in connection with the inclined axes spinning flanging head 20, the invention in its broadest context is to the specific areas of 65 improvement added to inclined axes spin flanging heads. It is desired that the claims which follow cover any design or use for such a head which includes the novel and unique improvements herein disclosed. 70 The inclined-axis spin head apparatus and the spin head per se are the subjects of the claims in our GB patent application No. 8131566 (Serial No. GB 2,092,492A) from which the present application is divided.

75

Claims (3)

1. A method for spin flanging a hollow thin walled cylinder, including the steps:

(i) arranging an inclined-axes spin flanging 80 head for rotary and axial movement in alignment with the axis of the hollow thin wall cylinder,

(ii) supporting said cylinder in axial alignment with said rotary axis of the spin

85 flanging head,

(iii) moving the spin flanging head axially into engagement with an open end of said hollow thin wall cylinder with a constant velocity, and then spin-forming the end edge of

90 the cylinder by

(iv) engaging rollers mounted to rotate on said inclined axes with the said edge of said cylinder, the rollers including surfaces which, in the course of the said constant velocity

95 movement, first flare and then radially form a flange on the said edge.

2. The method of claim 1, wherein the flaring is performed by a rim portion of each roller and the flanging is performed by a main

100 body portion of each roller, there being a transition curvature between the rim body portions of each roller of about 0.070 to 0.090" (1.78 to 2.28 mm).

3. A method of spin flanging according to 105 claim 1 and substantially as herein described with reference to and as shown in Figs. 2 to 4 of the accompanying drawings.

Printed in the United Kingdom for

Her Majesty's Stationery Office, Dd 8818935, 1985, 4235. Published at The Patent Office, 25 Southampton Buildings,

London, WC2A 1AY, from which copies may be obtained.